Scott is the owner of a tool and die shop. He has hired you to check his machine's calibration prior to starting production on a large order. To check this, you set the machine to create 1.5 inch screws and manufacture a random sample of 200 screws. That sample of screws has an average length of 1.476 inches with a standard deviation of 0.203 inches.

Does this sample provide convincing evidence that the machine is working properly or should it be shut down for repairs? Justify your reasoning mathematically.